ArmVirtPkg/ArmVirtQemu: hook NvVarStoreFormattedLib into VariableRuntimeDxe

ArmVirtPkg/ArmVirtQemu: hook NvVarStoreFormattedLib into VariableRuntimeDxe

In spite of both ArmVirtQemu and ArmVirtQemuKernel formatting the variable
store template at build time, link NvVarStoreFormattedLib into
VariableRuntimeDxe via NULL class resolution on both platforms. This lets
us test the depexes implemented in the previous patches.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Leif Lindholm <leif.lindholm@linaro.org>
Cc: Steve Capper <steve.capper@linaro.org>
Cc: Supreeth Venkatesh <Supreeth.Venkatesh@arm.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>